• Fabricating low-cost, high-performance, scalable polypropylene (PP)@graphene (G) nanocomposites from recycled PP fibers in waste masks by a simple electrostatic self-assembly hot-pressing method.
• The resultant PP@G presents a high thermal conductivity of 87 W m−1 K−1 and a high electromagnetic interference shielding effectiveness of 88 dB (1100 dB cm−1).
• Life cycle assessment and techno-economic assessment demonstrate significant environmental and economic advantages over existing waste mask disposal methods.
• This upcycling strategy offers a facile and promising approach to repurposing fibrous waste plastics for advanced thermal management and EMI shielding applications.